The Earth Science Picture of the Day (EPOD) highlights the diverse processes and phenomena which shape our planet and our lives. EPOD will collect and archive photos, imagery, graphics, and artwork with short explanatory captions and links exemplifying features within the Earth system. The community is invited to contribute digital imagery, short captions and relevant links.

Blue Moon Over Vecses, Hungary

The photo above shows a captivating blue Moon as viewed from Vecses, Hungary. On May 21, Saharan dust was blown north over central Europe. During the day, the micron-sized dust particles in the upper atmosphere caused Bishop's ring to appear around the Sun - a huge (about 28°) aureole coloured bluish-white inside and ochre outside. That night, the dust produced a spectacularly blue Moon -- a particularly rare sight. Particles having radii of approximately 600 nanometers scatter longer wavelengths (red light) more effectively than the shorter wavelengths (blue light). As a result, when particles of this size are found in the atmosphere, the disk of the Moon or Sun will have a decidedly bluish hue.